Modify HttpRequestTemplate and HttpResourceGroup to be DI friendly

To enable ribbon in Guice just add RibbonModule() when creating the injector (either via Guice or Governator).  Alternatively one can override the bindings for HttpResourceGroupFactory and HttpRequestTemplateFactory to override HttpResourceGroup and HttpRequestTemplate. 
Is it the plan to have single RibbonResourceFactory for all possible protocols, or we should have a corresponding class hierarchy like for ResourceGroup class.